The invention is related to providing a ball joint assembly disposed between a connecting rod and a piston to smoothly convert rotational motion of a crankshaft into reciprocating motion of a piston, and particularly to providing a ball joint assembly including a ball head of a connecting rod mounted on the safety seat of a piston, in the manner that a flexible member is flexibly supported against the ball head, thereby reducing the vibration and noise from friction between the safety seat and the ball head and having a relatively higher efficiency in operation.
The invention is particularly adapted to a compressor such as an air conditioner, etc.
In a conventional ball joint assembly as shown in FIG. 5 and FIG. 6, a ball joint assembly comprises a piston 31 and a connecting rod 32 with a ball head 32a formed on its one end, in which the piston 31 is provided with a sleeve 36 formed around its circumferential wall and a safety seat 33 formed on its central portion to receive the ball head 32a, both of which are respectively protruded from the rear end of the piston 31. The safety seat 33 includes a projecting section 33a protruding backward therefrom, a wear resistant resin 34 attached to the inner wall of the projecting section 33a and a hole 35 formed at a predetermined place near the base of the protruded safety seat 33. Therefore, as the ball head 32a is fitted into the safety seat 33, a caulking of the projecting section 33a against the ball head 32a, together with the wear resistant resin 34 is performed to freely rotate the ball head 32a therein.
Nevertheless, the conventional ball joint assembly has problems as follows: during caulking, the projecting section 33a seldom supports the ball head 32a at the exact position to be seated due to uneven pressure against the ball head 32a, it forces the available surface of the ball head 32a to be unevenly contacted with the surface of the projecting section 33a, thereby causing an uneven wear at the ball head 32a or the ball seat 33.
Furthermore, if the projecting section 32a is subjected to excessive force during caulking to tightly press the ball head 32a into the ball seat 33, it produces overheating during rotation of the ball head 32a. That is, the excessive caulking causes a piston connecting device to require a relatively higher load. With this, no play occurs between the ball head 32a and the ball seat 33. It blocks the flowing of lubricants into a gap between the ball head 32a and the ball seat 33 through the air hole 35.
Also, the area of the projecting section 33a is sized to the ball head 32a to prevent its escape from the ball seat 33 and therefore, exposure of the ball head 32a with respect to the lubricants is decreased.
Due to this, an oil film is not formed at the inner surface of the ball seat 33, and results in overheating at the ball seat 33 during the sliding of the ball head 32a.
The faster the rotating speed of a motor, transmitting its rotating force to the connecting rod 32 is, the higher the frictional energy of the ball head 32a in the ball seat 33. For example, the speed is about 3,500 revolutions per minute (rpm) at 60 Hertz per second. A relatively higher frictional energy causes an extremely uneven wear at the ball seat 33 and/or the ball head 32a. As a result, excessive play takes place between the ball seat 33 and the ball head 32a. Furthermore, since the projecting section 33a is made of steel having a relatively higher rigidity, a gap formed between the ball head 32a and the ball seat 33 can not be removed due to the limitation of the caulking of the projecting section 33a against the ball head 32a. Therefore, a hammer therefore, a hammer hitting phenomena of the ball hitting the ball head 32a against the ball seat 33 during operation, generates noise and vibration of the ball head 32a.